In 1967, G. Koster and G. Schmuckler published an article entitled: SEPARATION OF NOBLE METALS FROM BASE METALS BY MEANS OF A NEW CHELATING RESIN. In the article is a description of a synthesized resin having isothiourea groups that form a chelating group exhibiting an adsorption capacity for noble metals, platinum and gold. The resins described in this article have been determined to have an adsorption capacity in a ratio of gram of noble metal to gram of resin of 1.1 for gold, of 0.218 for palladium and of 0.488 for platinum. Because the described isothiourea groups are easily hydrolyzed, this resin is unstable in an alkaline medium.
In 1986, Patent No. CN 85,100,246 was issued in China. In this patent is described a series of aminoisopropyl mercaptan type cross-linked chelating resins. These resins were prepared by reacting 2-chloromethylthiirane with polyethylene polyamines. The adsorption capacity of the resins described in this patent is (g/g-resin): Au 1.0-1.1, Pd 3.0-4.5, Pt 4.0-5.0.
In 1990, S. H. Dong reported chelating resins bearing dithiocarbamate groups. The resins were synthesized by reacting carbon disulfide with a polymer containing secondary amino groups prepared from polyethylene. polyamine and 2-chloromethylthiirane. The adsorption capacity of the resins described in this article is up to (g/g-resin): Au 2.6, Pt 0.51. However, because the dithiocarbamate group is unstable in an acidic medium with a pH of 4 below. These resins are only used in an alkaline medium and a dilute acid.
This invention relates to the syntheses of a series of new chelating resins containing nitrogen and sulfur or oxygen atoms, which exhibited excellent adsorption properties for the noble metals such as gold(III), palladium(II), platinum(IV), silver(I), rhodium(III) and ruthenum(III). A fact worth mentioning is that adsorption capacity of them is more than that of the resins reported in the literature up to now. As for example, the capacity of the resin synthesized in this invention for noble metals is up to (g/g-resin): Au 2.6, Pd 0.9, Pt 0.6. The adsorption percentage of the most chelating resins for gold(III), palladium(II), and platinum(IV) are almost 100% from dilute solution containing noble metal, whereas for rhodium(III) and ruthenium(III) are 96.0% and 93.5% respectively. On the other hand, they exhibit high selectivity for noble metals, because of the adsorption ability of these resins for noble metals is strong, whereas for base metals is very weak. For example, from an aqueous solution containing gold(III), copper(II), iron(III), zinc(II), potassium(I) and sodium(I), only gold can be quantitatively adsorbed by the resin even though the concentration of these base metals is more than 15-50 times that of gold(III).
It is obvious that the chelating resins of this invention can be used effectively for separating, recovering and enrichment gold, palladium, platinum from industrial waste liquor or stock containing noble metals.